Tracked vehicle suspension

ABSTRACT

A suspension system for tracked vehicles especially small snowmobiles, which has longitudinally aligned skid elements that are articulated to one another and are resiliently held against the inside surface of the ground engaging portion of the track.

United States Patent Perreault et al.

[ 51 Apr. 25, 1972 TRACKED VEHICLE SUSPENSION Inventors: Jules Perreault, Sherbrooke, Quebec; Bertrand Southiere, Granby, Quebec, both of Canada Assignee: Bombardier Limited, Valcourt, Quebec,

Canada l-ileili Sept. 28, 1970 Appl. No.1 76,207

Related US. Application Data Continuation of Ser. No. 794,628, Jan. 28, 1969, abandoned.

Foreign Application Priority Data Jan. 10, 1969 Canada ..39,810

US. Cl. ..305/24, 180/5 R, 305/27 Int. Cl ..'....B62d 55/10 Field of Search ..180/5 R; 305/24, 27, 35 EB [561 References Cited UNITED STATES PATENTS 1,297,104 3/1919 Colahan... ..305/27 1,885,486 11/1932 Smyth.... ..305/27 X 2,284,075 5/1942 Tucker 180/5 3,485,312 12/1969 Swensonm. ..,.180/5 3,545,821 12/1970 Erickson 180/5 R 2,339,886 1/1944 Shannon ..180/5 FOREIGN PATENTS OR APPLICATIONS 151,835 3/1932 Switzerland ..305/27 Primary ExaminerRicha'rd J. Johnson Attorney-Smart & Biggar and Larson, Taylor and Hinds ABSTRACT A suspension system for tracked vehicles especially small snowmobiles, which has longitudinally aligned skid elements that are articulated to one another and are resiliently held against the inside surface of the ground engaging portion of the track. v 1

4 Claims, 7 Drawing Figures PATENTEIJAPRZSIBTZ 8,658,392

ShEET 1 OF 2 INVENTORS JULES PERREAULT BERTRAND SOUTHIERE BY F ATTORNEYS.

PATENTEnAPflzs I972 3,658,392

sum 20F 2 LINE INVENTORS JULES PERREAULT BERTRAND SOUTHIERE BYM 3 ATTO NEYS l I TRACKED VEHICLE sUsPE sioN I This is a continuation of Sen- No. 794,628, filed Jan. 28, 1969 now abandoned, U

I 1' su MAnY or "rt-is INVENTION I As iswell known in the art, means must be provided forap- .plying the weight of a tracked 'snow vehic le, eLg. large, passenger snowmobiles and small snowmobiles upon the .ground engaging portion of the track in as" uniform-a manner as possible. To this-effect wheel bogies can be used which carry oneor more relatively small wheels or alternatively skids, that contact the upper Surface ofthe ground engaging portion of the track. I

In the case of small snowmobiles (hereinafter referred to as snowmobilesj bogywheels are used nearly exclusively. This system when properly designed affordsgood traction I and does not. necessitate use of objectionablyheavy suspen sion components. Unfortunately for. a sufiiciently uniform wheels in rotation becomessignificant. i I, I I

;It has therefore been proposed to replacethe bogy wheels by skate-like skid members, and asnowmobile usinga skid suspension'has been used commercially. This prior'arrangement incorporates two side by side rigid skids extending'along the entire lengthof the ground engaging portion of the'track and interconnected to one another so as to form a rigid chassis whichfis resiliently supported to the frame of the snowmobile. With this structure, which is relatively heavy,.the ground engaging portion of the track presents itself as a flat surface (which cannot bebent in the longitudinal direction; as a result 1 the arrangement cannot follow the contour of uneven grounds as can the above noted bogy wheel suspension system, and the traction of the track with a snow surface suffers. Nevertheless this rigid skid suspension does away withamultiplicity of parts such as wheels and bearing and offers a smoother ride than wheel bogy suspensions. I v

The object of this inventiontherefore is to provide a skid suspension for tracked vehicles, especially snowmobiles, which combines the advantages of the above noted prior skid suspension withthe 'superiontraction and lightness of the widely used bogy wheel suspension systemsi We have found that this can be achieved by providing skid means combined with suitable lever means andspring means, wherein the skid means includes at leasttwo skid members which are articulated to one another.

With this suspension system the ground contacting track portion can yield longitudinally to accommodate for ground irregularities, and better traction than with the noted prior rigid skid arrangement, can be obtained. We have also 7 discovered that with this articulated arrangement the suspension design can be substantially simplified and when compared with said rigid skid design a 2:1 weight gain is possible.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side view of a suspension system as installed on a snowmobile; V 1 i FIG. 2 is a perspective view of the suspension shown in FIG.

FIG. 4; and

F IGS 6 and 7 are schematic representations of thesuspension system of FIG.,1, over different ground irregularities.

With reference to the accompanying drawings FIG. 1 illustrates a suspension system for supporting a snowmobile frame 10"upo'n the lower, ground-engaging portion of endless track 12. The suspension-system asshownin FIGS. 1, 2 and 3 comprises a pairof leading wheels 20, 21 which bear against the insidesurface of track 12', and which may be rotatably connected to the leading portion ofskids 31. Each skid 30, 31 inthe illustrated embodiment incorporates two skid members 35', 36 which extend in longitudinal direction of track 12 and are articulated to one another as shown at 38. Thejeading end of the front skid member 35, is rigidly connected to the mounting means-of leading wheels and 21 and the trailing end of the rear skid member 36 is left more or less free to ride on the belt although, as will be seenzhereinafter, subjected to the ac.- tionof torsion-springs, a

In order to, mount'the-skid .rnembers. and 36 onto the frame of the vehicle 10 a number of supporting arm assemblies" (four being used in the illustrated embodiment 40, 41, 42 and 43) which are pivotally connected to frame 10 by means of cross-shafts 50, 51, 52 and-53 and project generally rearwardly and downwardly therefrom to meet skid members 35 and 36as shown at 61', 62 and 63. Each supportingarm assembly 40, 41, 1421or 43 is urged downwardly in a clockwise directionas seen in F IG. 1 by means of torsion springs 70, 71, 72 and I 73, and as illustrated these torsion springs ,can be formed of coiled spring wires having their respective end por tions retained to the frame ltl and tea part of the associated supporting arm assembly40, 4l, 42 or 43. Hence, with this arrangernent the ground engaging portion of track 12 is resiliently maintained ata suitable distance from the underside of framev 10, andby properly selecting the gauge of torsion springs 70 to 73 and adjusting the length and the angle of the supporting arm assemblies to 43, the body of vehicle 10 can be kept a safe, predetermined distance from the ground in the rest and travelling conditions. v Y I It. will therefore be appreciated that with the above described arrangement, the skids which'define a generally flat configuration when vehicle 10 is riding over plane ground, can

accommodate for substantial ground irregularities as is clearly I illustrated in FIGS. 6 and7. Furthermore, the occurrence of a depression or bump on the ground when the vehicle is moving will first deflect leading wheels 20 and 21 together with the leading end of the front skid member 35, thereafter will raise the inter-connected portions of skid members 35 and 36 and finally, raise a trailing end of rear skid member 36 in succession without significantly affecting the generaldirection of movement of vehicle 10. This particularly desirable feature which is due to the fact that each skid member is free to move relative to the frame of the vehicle'and relative to the other skid member on the same side, enables the suspension system to actually absorb slight ground irregularities and average" more substantial ones, thereby giving the impression to the operator that the vehicle 10 is floating over the ground especially at higher speeds.

Another important feature of this suspension system over the above mentioned prior skid suspension arrangement is that when proceeding in fairly depi 'sno'wflli'e" leading ends of the front skid member 35 on each sideof vehicle 10 tend to leave the ground slightly while therear skid members 36 remain generally horizontally, with the results that the leading portion of the ground engaging part of the track 12 assumes a certain angle of attack that enables the vehicle 10 to float over the snow and consequently, facilitates manoeuvering and enables higher speed. I

Referring again to FIGS. 1, 2 and 3, each supporting arm assembly 40 to 43 comprises an upper cross tube 90, 91, 92 and 93 mounted around cross shaft 50 to 53 (see FIG. 3) and a one of their ends suitably coupled to the intennediate portion of the arms of the assemblies 40 to 43 by means of tabs.

The leading support arm assembly 40 is also pivotally connected to the leading wheels 20 and 21 and to the leading end of front'skid member 35 as at the ends of cross bar 60, cross bar 60 being welded just behind the upwardly curved portion of skids 35. Due to the geometry of the arrangement and in order to enable the skid members 35 and 36 to yield to ground irregularities in the manner mentioned hereinabove, the different mounting arrangement must be provided at the connection of the lower end of the supporting armassemblies 41, 42 and 43 with'the associated sections of skid members 35 and 36. In fact, it should be apparent that the arms of supporting assemblies 41, 42 and 43 must be slidably connected to skid members 35 or 36 or alternatively these arms should be in the form of telescopic members. However it is preferred to use a sliding arrangement as is shown in detail in FIGS. 4 and 5. v

Referring therefore to FlGS. 4 and'5, a'slide shoe 200 is fixed to an appropriate portion of the skid members 35 or 36 and a runner 210 is articulated to the associated arm of the supporting arm assembly 41, 42 or 43. Specifically, slide shoe 200 is in the form of an elongated constant cross-sectionelement while runner 210 is formed of an elongated C-shaped section having an upper portion 211 with side wings 212 terminated at their lower portions with inwardly directed flanges 213. The inside dimension of the C-shaped channel member 210 is adapted to closely fit around slide shoe 200 thereby permitting longitudinal displacement of runner 210 with respect to slide shoe 200. On the upper part of runner 210 is provided a U-shaped connector 220 which is adapted to pivotally receive the lower end of the associated arm 901 etc. which in turn is provided with a transverse sleeve 225 which receives a tubular bushing 230. The assembly may be bolted together as shown at 240.

With this arrangement, the lower end of each arm is free to reciprocate longitudinally with respect to the associated skid member over the entire length of the slider shoe 200 which of course can be made as long as desired. Furthermore the sliding action of runners 210 and consequently the free displacement of each skid member 35, 36 in a vertical plane are facilitated by mounting the supporting arm'assembles 40 to 43 in a trailing configuration with respect to their cross shafts 50 to 53.

The structure of skid members 35 and 36 can advantageously consist of a box-shaped channel 300 to the underside ofwhich an elongated blade 310 is affixed such as by rivets as shown at 320. Preferably the blade member 310 may be of generally rectangular cross section with a recess on the upper portion for receiving the underside of box-shaped channel 300. In a preferred embodiment, blade 310 is made of hard, slippery, wear resistant plastic materials, for example ultra high molecular weight polyethyleny, polyurethene, nylon and materials known under the trademark Teflon." To

reduce wear and friction the track 12 can be provided with rows of metallic pressure memb'ers disposed on the inside surface thereof such as for example metallic cleats 160 as are already provided between the successive sprocket teeth holes 150 of most conventional snowmobile tracks. The material of slider shoe 200 can also be a hard, slippery, wear resistent plastic material and, as illustrated in FIGS. 4 and 5, the boxshaped channel 300 can be sandwiched between the plastic members 310 by means of sunk rivets 320 extending through the entire assembly. I

It will be appreciated that the invention is not limited to pairs of articulated skid members 35 and 36 as more than two longitudinally aligned skid members could be installed with one or more individual supporting arm assemblies, along the length of each skid member and/or at the points of connection therebetween.

What we claim is:

l. A snowmobile suspension for mounting on the frame of a snowmobile and adaptedto apply a substantial part of a snowmobiles weight upon the ground engaging portion of the track thereof, comprising at least two spaced parallel skids extending along asubstantial portion of the length of the ground engaging portion of said track, at least two supporting arm assemblies extending between the bottom of the frame of said snowmobile and different spaced apart regions of said skids, pivotal means for pivotally connecting said supporting arm assemblies to the bottom of said frame and to each of said skids, one of said supporting arm assemblies being fixed against longitudinal movement relativeto said skids while the other has elements movable with respect to said skids, spring means acting upon said supporting arm assemblies to resiliently maintain said frame a predetermined distance above said skids, each said skid consisting of at least two skid members articulated to one another in an end-to-end relationship and free to move relativeto said frame in a vertical plane parallel to the length of said track under the action of said spring means and the weight of said snowmobile.

2. A suspension as defined in claim 1, wherein each said supporting arm assembly comprises at least one arm extending downwardly and rearwardly with respect to said frame, the lower end of said arm being coupled with one of said skid members.

3. A suspension asdefined in claim 2, wherein the coupling of the arm of the leading supporting arm assembly consists of a pivotal connection with the associated skids, the arms of the other supporting arm assemblies being coupled to the adjacent skid members by means of a pivotal sliding arrangement allowing reciprocation of the lower end of the associated arm along the longitudinal axis of said adjacent skid member.

4. A suspension as defined in claim 1, further comprising a leading wheel mounted for rotation upon the inside surface of said track immediately in front of each said skid. 

1. A snowmobile suspension for mounting on the frame of a snowmobile and adapted to apply a substantial part of a snowmobile''s weight upon the ground engaging portion of the track thereof, comprising at least two spaced parallel skids extending along a substantial portion of the length of the ground engaging portion of said track, at least two supporting arm assemblies extending between the bottom of the frame of said snowmobile and different spaced apart regions of said skids, pivotal means for pivotally connecting said supporting arm assemblies to the bottom of said frame and to each of said skids, one of said supporting arm assemblies being fixed against longitudinal movement relative to said skids while the other has elements movable with respect to said skids, spring means acting upon said supporting arm assemblies to resiliently maintain said frame a predetermined distance above said skids, each said skid consisting of at least two skid members articulated to one another in an end-to-end relationship and free to move relative to said frame in a vertical plane parallel to the length of said track under the action of said spring means and the weight of said snowmobile.
 2. A suspension as defined in claim 1, wherein each said supporting arm assembly comprises at least one arm extending downwardly and rearwardly with respect to said frame, the lower end of said arm being coupled with one of said skid members.
 3. A suspension as defined in claim 2, wherein the coupling of the arm of the leading supporting arm assembly consists of a pivotal connection with the associated skids, the arms of the other supporting arm assemblies being coupled to the adjacent skid members by means of a pivotal sliding arrangement allowing reciprocation of the lower end of the associated arm along the longitudinal axis of said adjacent skid member.
 4. A suspension as defined in claim 1, further comprising a leading wheel mounted for rotation upon the inside surface of said track immediately in front of each said skid. 